Fire detector cable



W. J. TURENNE FIRE DETECTOR CABLE Filed April 19, 1941 March 10, 1942.

Patented Mar. '10, 1942 UNITED .STATES PATENT orics FIRE DETECTOR CABLE Wilfred J. Turenne, Fayville, Mass.

Application April 19,1941, Serial No. 389,399

11 Claims.

nomically, that will have high sensitivity to a,

rise in temperature, that may be subjected for an indefinite period without deterioration to temperatures that would destroy a detector cable including in its construction insulating material of organic matter, and that will be immune to injury by vibration of the most excessive character;

in the preferred form of my invention, a tube of easily fusible material encloses a conductor formed of a metal having a relatively high point of fusion, such as copper, on which are placed spaced insulating elements which aremaintained in position by any suitable means whereby air spaces are provided between the tube and the conductor and each pa r of insulating elements, into which space the molten metal of the tube will iow when the temperature of the air surrounding tube, or the temperature of the object against which it is placed, exceeds the fusion point thereci. any suitable detecting device may be connected electrically to the tube and conductcr enclosed therein, preferably to the respective ends thereof.

In the drawing accompanying and forming a part 01' this specification,

Figure l is a longitudinal central section,

somewhat diagrammatic in nature, representing one way in which my improved fire detector cable may be made. I

Fig, 2 is a longitudinal section of a fire detector cable embodying my invention.

Fig. 3 is an end View of one of the grooved rolls shown in Fig. 1.

Fig. 4 is a longitudinal central section on an enlarged scale or a modification.

Fig. 5 is a plan View of the insulating bead shown in Fig. 4.

In the particular drawing selected for more fully disclosing the principle or my invention, I0 is a cylindrical conductor of easily fusible metal or alloy'of any suitable character enclosing a number oi longitudinally spaced insulating elements ii, which may be beads formed of glass or any other suitable material, said elements being apertured and the conductor II of copper or other suitable material passing through the apertures therein.

While any suitable means may be employed for maintaining the spacing of the beads, I prefer, as illustrated, to have the same partially imbedded in the inner wall of the tube !0.

Whatever'may' be the means used for maintaining the longitudinal spacing of the beads, there will be an air space l3 between each pair of heads, the interior wall of the tube and said conductor, which space will be filled, or partially filled, with the metal of the tube when a portion of the latter is melted by a sufl'icient rise in temperature in the vicinity thereof, and thereby a circuit, including said tube, conductor, indicating device H and electrical source IE will be closed.

Although suitable for general fire detecting use, my invention is particularly applicable to use in aeroplanes, and in such case, the cable may be located on the outer edge oi the fire wall behind the engine. In such location, the cable will be subject to a relatively high air pressure caused by the travel of the plane at high speed, and as such air pressure would be likely to blow the molten metal of the tube away from the inner conductor without making electrical contact therewith, I have found it desirable to provide the outer wall oi the tube with a thin plating 263 of a metal having a fusion point higher than that of the metal or alloy of the tube, such, for example, as nickel. it has been found that a layer of nickel not more than .993" will suillce for this pulpose.

While it is highly desirable that the outside conductor ll! be made of fusible metal, from the viewpoint of extreme sensitivity to undesirable and dangerous temperature increases, it is nevertheless feasible to make the inner conductor :12 of a metal or an alloy having a relatively low point of fusion, and the outside conductor of a metal having a relatively high fusion point.

It will be manifest that continuous fire detect-= ors are highly advantageous, as compared to thermo switches, thermocouples, and the like, which are local in their action, for a detector of the continuous type, such as described herein, would indicate a small fire at any point in the area in which the cable is placed.

A convenient and efiicient way of making my improved fire detector, consists in stringing a number of apertured elements, such as the glass beads I i, on the central conductor l2 and then enclosing such string within a metallic tube Iii, the inner diameter of which is substantially equal to, or preferably slightly larger than, that of said beads, as shown in Fig. 1. The diameter of the tube is then reduced by passing the tube through grooved drawing rolls IS, the groove l'l of which has, of course, a diameter somewhat time, the peripheral portions of the beads contiguous to the-inner walls of the tube will be partially imbedded therein and the longitudinal" spacing of the beads will be maintained.

The spreading of the beads, if effected in the manner above described, will be facilitated by in the further spreading of-the beads from one another longitudinally and in partially imbedding them in the inner wall of the tube. Alternatively, by means of the projections ll, the

desired spacing and separation of the beads, or.

other insulating elements, maybe eifected and maintained without drawing down the tube after the string of initially spaced insulating elements has been placed therein. 7

It is to be understood that my invention and method are not to be confined to the illustrative embodiments herein shown and described, for both are subiectto a wide range of variation within the purview of the appended claims.

I claim:

1. As an article of manufacture, a tube -of fusible metal, aplurality of longitudinally spaced apertured elements of insulating materialv en closed within said tube and a metallic conductor passing through the apertures in said elements and extending throughout the length' of said tube, said conductor being electrically insulated from said tube by said elements. v

2. As an article of manufacture, a tube of fusible metal, a plurality of longitudinally spaced apertured elements of insulating material enclosed within said tube and partially imbedded within the. inner wall'thereof, and a metallic conductor passing through the apertures in said elements and extending throughout the length of said tube, said conductor being electrically insulated from said tube by said elements.

3. As an article of manufacture, a tube of fusible metal, a plurality of longitudinally spaced apertured beads of insulating material enclosed within said tube and disposed substantially coaxially therewith and a metallic conductor passing through the apertures in said beads and extending throughout the length of said tube, said conductor being electrically insulated from said tube by said beads.

, 4. Asan article of manufacture, a tube of metal having a relatively low point of fusion, the outer walL of which is platedv with'a thin layer of a metal having a fusion point higher than that of the metal of said tube, a plurality of longitudinally spaced apertured insulating'elements enclosed within said tube, and a metallic conductor passing through the apertures in said elements and extending throughout the length if said tube, said conductor being electrically insulated from said tube by said elements. .1

5. As an article of manufacture, a metallic tube, a plurality of longitudinally spaced apertured elements of insulating material enclosed within said tube and partially imb'edded within the inner wall thereof, and a metallic conductor means for maintaining the spacing of said insulating elements longitudinally ofsaid conductor, said conductor being electrically insulated by said elements from said tube and having a point of fusion substantially different therefrom.

7. As an article of manufacture, a tube of fusible metal, a plurality of apertured elements of insulating material enclosed within said tube.

each provided with a projecting portion extending in the direction of the aperture therein and contacting one of the elements next adjacent thereto, and a metallic conductor passing through the apertures in said elements and extending throughout the length of said tube, said conductor being electrically insulated from said tube by said elements;

8. As an article of manufacture, a tube of fusible metal.-the outer wall of which is plated with a thin layer of a metal having a fusion point higher than that of the metal of said tube, a plurality of longitudinally spaced apertured elements of insulating material enclosed within said tube and a metallic conductor passing through the apertures in said elements and extending throughout the length of said tube, said conductor being electrically insulated from said tube by said elements.

9. As an article of. manufacture, a tube of fusible metal, the outer wall of which is plated with a thin layer of a metal having a fusion point higher than that of the metal of said tube. a plurality of longitudinally spaced apertured elements of insulating material enclosed within said tube and partially imbedded within the inner wall thereof, and a metallic conductor passing through the apertures in said elements and extending throughout the length of said tube, said conductor being electrically insulated from said tube by said elements.

10.'As an article c1 manufacture, a tube of fusiblemetal the outer'wall of which. is plat ed with a thin layer of a metal having a fusion point higher than that of the metal of'said tube. a plurality of longitudinally spaced apertured beads of insulating material enclosed within said tube and disposed substantially coaxially therewith and a metallic conductor through the apertures in said beads and extending throughout the length of said tube,'sa id conductor being electrically insulated from said tube by said .11. As an article of" manufacture, a tube of fusible metal. the outer wall of which is plated with a thin. layer of a metal having a fusion point higher than that of the metal of said tube. a plurality of apertured elements of insulating material .enclosedwithin said-tube, each provided with a projecting portion extending in the passing through the apertures in said elements I and extending throughout the length of said tube,

direction of the aperture therein and contacting one of the elements next adjacent thereto, and 1 a metallic conductor passing through the apertures in said elements and extending thro ahout the length of said tube. said conductor being electrically insulated from said tube by said elements.

' WILFRED J. TURENNI. 

